- Department of Neurosurgery, David Geffen School of Medicine at UCLA, 757 Westwood Plaza, Suite 6236, Los Angeles, CA, 90095-7436, USA
Correspondence Address:
Neil A. Martin
Department of Neurosurgery, David Geffen School of Medicine at UCLA, 757 Westwood Plaza, Suite 6236, Los Angeles, CA, 90095-7436, USA
DOI:10.4103/2152-7806.109810
Copyright: © 2013 McLaughlin N This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.How to cite this article: McLaughlin N, McArthur DL, Martin NA. Use of stent-assisted coil embolization for the treatment of wide-necked aneurysms: A systematic review. Surg Neurol Int 30-Mar-2013;4:43
How to cite this URL: McLaughlin N, McArthur DL, Martin NA. Use of stent-assisted coil embolization for the treatment of wide-necked aneurysms: A systematic review. Surg Neurol Int 30-Mar-2013;4:43. Available from: http://sni.wpengine.com/surgicalint_articles/use-of-stent-assisted-coil-embolization-for-the-treatment-of-wide-necked-aneurysms-a-systematic-review/
Abstract
Background:The use of stent-assisted coiling (SAC) has been shown to be a treatment option for complex aneurysms. We reviewed systematically the immediate and mid-term angiographic results following treatment of wide-necked aneurysms with self-expanding stents and coils, as well as the peri- and postprocedural rate of complications.
Methods:A computerized database search was conducted from 01/2000 to 04/2011 using appropriate indexed terms on Pubmed. Inclusion criteria were: (1) homogeneous populations of ≥10 patients with wide-necked aneurysms; (2) use of a self-expandable neurovascular stent and coils for aneurysm treatment; (3) immediate and follow-up angiographic results; and (4) periprocedural and delayed thrombotic complications.
Results:Seventeen studies were included, containing retrospectively collected data on 656 patients/702 aneurysms. The target aneurysm was located on the anterior circulation in 78.4% of patients. The immediate rate of complete occlusion was 46.3%, (19.3-98.1%). The intra- and postprocedural rate of intrastent thrombosis or thromboembolic event was 4.6% and 4.3%, respectively. Complete occlusion was documented in 71.9% at last angiographic follow-up. The rate of recanalization was 13.2% of aneurysms (0-28.8%). Delayed in-stent stenosis occurred in 5.3% cases (0-20.6%).
Conclusion:SAC has been considered a treatment option for selected wide-necked aneurysms in some institutions. The use of intracranial stents should take into consideration the risk of ischemic complications, recanalization, delayed in-stent stenosis; and the currently unknown lifetime risks for stenosis, vascular injury, device failure, and aneurysm recurrence related to intracranial stenting. There is an evident need for a prospective multicenter registry for all treated patients with SAC.
Keywords: Aneurysm occlusion, complication, intracranial aneurysm, intracranial stent, wide neck aneurysm
INTRODUCTION
Since the introduction of the Gugliemi detachable coil (GDC) system in the early 1990s, the criteria for endovascular treatment have broadened. Embolization with GDCs alone is a recognized effective and durable treatment option in most small aneurysms with small necks. However, in the setting of wide-necked, large, or giant aneurysm, important technical limitations in the GDC technology has prevented complete and durable aneurysm occlusion.[
In the late 1990s and early 2000s, intracranial neurovascular stents were introduced to the armamentarium of endovascular surgery to treat wide-necked aneurysms.[
Since their initial introduction, many improvements have been brought to the initial generation of neuroendovascular devices to improve their flexibility, maneuverability, and effectiveness [
Furthermore, our impression in rendering second opinions for aneurysm treatment over the past 5 years is that SAC and also stents alone are increasingly being recommended not only for inoperable wide neck aneurysms, but also for many surgically treatable wide-neck aneurysms. This experience prompted our review of the literature regarding results of SAC. The intent of this review is to define the current state of understanding of success and complication rates, to begin to define appropriate use, and to allow comparison with surgical results. As the new flow diverters, such as the Pipeline and Silk prototypes, constitute a distinct form of endoluminal reconstruction with still limited usage (i.e., indications with Food and Drug Administration [FDA]-approved indications), we have not included them in this review.[
METHODS
Research method
A computerized database search was conducted from January 2000 to April 2011 using appropriate indexed terms on Pubmed including “intracranial aneurysm”, “treatment”, “stents”, “intracranial stent”. As of April 2011, the search resulted in 896 abstracts. All abstracts of manuscripts published either in English or in French were reviewed. We obtained the full manuscripts for all case series reporting clinical and/or radiological data following intracranial stenting for the treatment of cerebral aneurysms that included 10 or more patients, or controlled clinical trials, or prospective studies. In cases of doubt or if information was missing to determine eligibility, the entire article was obtained and reviewed. A total of 73 manuscripts were retained and reviewed thoroughly. Reference lists of all these articles were checked manually for additional potential eligible studies.
Inclusion/Exclusion criteria
Inclusion criteria were: (1) homogeneous populations of 10 or more patients with wide-necked aneurysms specifically in the report's methodology section; (2) use of a self-expandable noncovered neurovascular stent for wide-necked aneurysm treatment; (3) description of delayed angiographic follow-up (6 months) data analyzed in regards to initial postprocedure results; and (4) enumeration of intraprocedural and postprocedural thrombotic complications. Studies were not eligible if (1) they were case reports or small case series (n < 10); (2) their population was not homogeneously composed of wide-necked aneurysm; (3) the main stent used was either a coronary stent, covered stent, or balloon expandable stent; (4) use of flow diverters;[
Data extraction
From the included studies, the following data were extracted: (1) number of participating patients; (2) number of aneurysms treated; (3) location of aneurysms (anterior circulation vs posterior circulation); (4) type of stent used; (5) occurrence of intraprocedural events specifically intrastent thrombosis or thromboembolism (asymptomatic and symptomatic events); (6) procedure-related mortality; (7) initial postprocedure angiographic result (complete occlusion rate); (8) postprocedural events, specifically intrastent thrombosis or thromboembolism (asymptomatic and symptomatic events); (9) follow-up angiographic results expressed as change in regards to the initial postprocedure result; (10) timing of follow-up angiography; (11) recanalization; (12) treatment required for recanalized aneurysm; (13) posttreatment in-stent stenosis (asymptomatic or symptomatic); (14) timing of diagnosis of in-stent stenosis; (15) treatment performed for in-stent stenosis.
Outcome measures
For the patient, the most important outcome is successful aneurysm occlusion. This includes complete (or near complete) occlusion at long-term follow-up, without significant recanalization, with no treatment-related symptomatic complications. Therefore, outcome was divided into three major components. The first outcome component is achievement of treatment goal – aneurysm occlusion. Most studies used the three point system developed by Roy, et al. to express the angiographic degree of aneurysm occlusion.[
Statistical methods
Proportions of successes or failures were calculated for each qualifying publication without adjustment, as were aggregate proportions in each of the outcome domains. Confidence intervals (95% CIs) for each proportion were calculated using the mid-P exact method.[
RESULTS
A total of 656 patients with 702 aneurysms were collected from the 17 studies included in this systematic review [Tables
Intraprocedural events including intrastent thrombosis and thromboemboli (TE) were reported in 16 studies (totaling 624 patients and 670 aneurysms), and were diagnosed in 4.6% of patients (29/624) and 4.3% of aneurysms (29/670). In these 29 patients with intraprocedural events, the majority had an intrastent thrombosis (22/29). The same 16 studies also reported their incidence of postprocedural stent thrombosis and TE events, resulting in 4.3% of patients (27/624) and 4.0% of aneurysms (27/670). The overall incidence of intrastent thrombosis and TE is 9.0% of patients (56/624) and 8.4% of aneurysms (56/670). The aggregate value of intraprocedural and postprocedural intrastent thrombosis and TE was, respectively, 0.0465 (95% CI: 0.0319-0.0652) [
Figure 1
Schematic diagram of proportion of events from selected publications. Proportion of events (successes or failures) (solid symbol and 95% CI), by selected publication ordered by publication date, and by aggregate event (open symbol and 95% CI). (a) Intraprocedural thromboembolic event, (b) Initial aneurysm occlusion, (c) Postprocedural thromboembolic event, (d) No change of angiographic findings at follow-up angiography, (e) Recanalization, (f) Delayed in-stent stenosis. Aggregate value and confidence interval given for each graph
The completeness of aneurysm occlusion immediately after treatment was assessed in cases that underwent a SAC treatment performed in one procedure. Of the 17 studies, 1 did not detail the immediate angiographic results[
Follow-up angiography was performed in all 17 studies using solely digital subtracted angiography (DSA) in 15 studies and DSA or magnetic resonance angiography (MRA) in 2 studies.[
Recanalization was assessed on follow-up angiography in all studies. Overall 13.2% (69/522) aneurysms presented some degree of recanalization on the follow-up angiogram, manifesting itself by a step-down on the three point aneurysm occlusion scale by Roy, et al.[
Presence or absence of delayed in-stent stenosis was clearly reported in 16 studies. The overall rate of delayed in-stent stenosis was 5.3% (27/512), with individual study rates varying from 0% to 20.6%. The aggregate value of this event was 0.05277 (95% CI: 0.0358-0.0748) [
DISCUSSION
Treatment options for wide-necked aneurysms
Treatment of wide-necked aneurysms has been challenging for neurosurgeons and interventional radiologists.[
Evolution of intracranial stents
The earliest clinical reports of SAC of an intracranial cerebral aneurysm date to the late 1990s, by Higashida, et al. and Mericle, et al.[
The initial studies assessing the use of each new stent have reported the feasibility of SAC for treatment of intracranial aneurysms. These studies from single institutions are numerous, and present results of small to medium size populations with various types of aneurysms including wide-necked, fusiform, and dissecting types.[
Summary of findings and implications of results
From the 17 studies that met the inclusion criteria, data were collected on 656 patients/702 aneurysms [Tables
The statistical analysis of the described results is limited. All of the above subgroups showed significant indices of heterogeneity (H, P < 0.001), representing high levels of disagreement across the qualifying sources assessed in each of the separate key topic areas. In addition, the presence of multiple zero cell counts precludes computation of meaningful odds outcomes, the preferred statistical approach to understanding descriptive binary outcomes in noncontrolled studies. Aggregate confidence intervals are likely to be underestimated due to this same problem. Regrettably, none of the qualifying studies provided sufficient basis to compute odds ratios for more refined statistical appraisal of the topic areas.
Limitation of the study
A critical review of the current literature is important to determine the current understanding of safety and durability of SAC, and identify limitations preventing extrapolation of results.
Publication bias – A key limitation of any literature review is “publication bias”. Studies with positive results tend to be published more often than those with equivocal or negative results.[
Type of studies included – The major limitation of this analysis refers to the retrospective nature of included studies, and the absence of a control group allowing comparison between SAC and traditional coiling. For the inclusion criteria detailed in this review, no prospective study or randomized trial was yet published in the literature. Even when considering other published series not included in the review, no study has yet determined superiority of SAC over traditional coiling or other treatment modality in terms of long-term durability.[
Background of treating physicians – Although the inclusion and exclusion criteria were designed to obtain the most homogeneous study population possible, there are some physician-related factors that cannot be accounted for in the results such as each treating team's decision making process as well as their personal experience with stenting techniques.[
Variety of stents and SAC protocols – Although most studies present results of the SAC using a specific type of stent, others included a variety of stents.[
The pre- and postprocedural antiplatelet/anticoagulation protocol used by different institutions may also vary. The dual antiplatelet regiment of acetylsalicylic acid and clopidogrel has become a recommended regimen as they act synergetically to reduce the chances of TE events and stent thrombosis.[
Shortcomings in reporting of results – Data analysis is limited by the data collected and reported in each individual study. In most studies, no clear or standardized definition was given for the events tabulated.[
Although the underlying pathology of the arterial wall is distinct, the literature on the treatment of obstructive coronary disease with intraarterial stents has been a launching point for many of the hypothesis regarding stenosis of intracranial arterial stents. Specifically for in-stent restenosis following percutaneous coronary intervention, the rates have passed from 30% to 50% in patients that underwent angioplasty without stenting, to 10-30% in those treated with an intravascular stent.[
Other large reports or reviews
Bodily, et al. reviewed the literature regarding SAC specifically in the context of acutely ruptured intracranial aneurysms.[
Summary and implications for selection of stent therapy for aneurysms
This review has reported the range of results, and across-series aggregate results, for SAC for intracranial wide-necked aneurysms. Since there is, as yet, no information on long-term, lifetime risks of arterial injury or stenosis, aneurysm recurrence, stent fracture, or vessel erosion, use of intracranial stents should employed very selectively for younger patients with a substantial life expectancy. Thus treatment decisions, and selection of a new technique (e.g., SAC), over an established technique (e.g., microsurgical clipping) should be made very cautiously, considering the documented limitations and complications, and unknown long-term results of the new technique – this is key particularly for optimal patient-centered care. Decision-making should not be based only on the results of the reports with the most favorable results – but should objectively consider the full range of reported results. Local decision-making should equally consider local results for the specific center where treatment is planned.[
The treatment of unruptured MCA aneurysms represents such an example. The presence of a wide neck and/or of an arterial branch originating from the aneurysm neck are two features that account for failure of standard endovascular techniques. In these circumstances, surgical clipping still represents the most efficient and durable treatment for unruptured MCA aneurysms.[
Further studies should take into considerations the discussed limits to help accurately define the role of SAC in the treatment of wide-necked aneurysms.[
ACKNOWLEDGEMENT
This research was supported by the Casa Colina-Neil Martin Fellowship Program at UCLA.
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